Orleans Harbormaster Dawson Farber told WBZ-TV a senior Orleans town lifeguard spotted a dorsal fin of a Great White Shark about 150 yards off the beach at about 10:15 a.m.

Farber said they have tens-of-thousands of seals in the harbor right now.

“You can understand why they’re here,” Farber said.

Farber said the shark was estimated to be between 12 feet and 13 feet long.

Swimmers were asked to get out of the water and surrounding towns and the Cape Cod National Seashore were notified.

“There are a lot of people down here, a lot are taking pictures of the newly constructed beware of the sharks sign,” John Oman , owner of Liam’s at Nauset Beach said. “The beach is open and people are in there with their wet suits.”

Although early in the season, Oman said beach goers don’t seem too nervous.

“I’ve had hundreds of people here at the restaurant today and not one has expressed fear of the sharks being out there today,” he said.

The shark was seen toward southern end of protected swimming area and headed in the direction of Chatham.

Swimmers must be kept out of the water for an hour after a confirmed sighting unless there is another sighting.

“We’re right at the beginning of what’s going to be a long summer,” Farber said.